In the production of nonwovens, it can be advisable, especially at high production speeds of >100 m/min, to provide a covering structure to cover the fiber web or the web of nonwoven conveyed on a transport device and thus to prevent the fibers from being blown about.
For example, a technology of this type has been used in crosslappers. Crosslappers serve to deposit the fiber web produced by a carding machine in multiple layers as uniformly as possible onto an output conveyor belt to obtain the web of nonwoven. The fiber web is usually guided first through an upper carriage and from there to a laying carriage, through the laying nip of which the fiber web is deposited onto the output conveyor belt. At least two fiber web conveyor belts are used to guide the fiber web through the crosslapper. The movements of the fiber web conveyor belts, of the upper carriage, and of the laying carriage are controlled in coordination with each other.
In the area extending from the infeed area of the crosslapper to the upper carriage, it is advantageous for the fiber web not just to rest on a web conveyor belt but also to be covered from above by a cover belt. In this way, the fiber web can be prevented from being blown about, and thus the uniformity of the deposited web of nonwoven can be ensured. Structures of this type are known from, for example, DE 195 43 623 A1, EP 1 136 600 A1, and EP 1 870 499 B1. The disadvantage of these crosslapper configurations is the complexity with which the endless cover belt is guided, which requires a large number of components and a great deal of mechanical effort.
U.S. Pat. No. 8,495,799 B2 discloses a simplified configuration of a crosslapper, in which the cover belt is provided with a smooth surface and is not moved concomitantly with the fiber web but rather serves, in effect, as a stationary cover over the fiber web. To ensure that the cover belt protects the fiber web on the fiber web conveyor belt for the longest possible time, the cover belt extends from an attachment point in the infeed area of the crosslapper through the upper carriage to a second attachment point at the other end of the crosslapper.
This configuration suffers from the disadvantage that, as the cover belt slides through the upper carriage, high relative velocities occur between the stationary cover belt and the upper carriage, which is moved transversely back and forth. This results in stress on the cover belt and increased wear, especially in the area of the reversal point of the upper carriage.